Systems and methods for identifying subtype, prognosis, and monitoring of breast cancer

A method of determining breast cancer subtype in a subject comprising:

• obtaining or having obtained an amount of a sample taken from a subject;
• isolating a population of extracellular vehicles (EVs) in the sample;
• identifying differential expression of one or more proteins or peptides in the isolated EVs as compared to an expression level of such EV proteins or EV peptides in a control;
• comparing the differential expression in the isolated EVs to one or more expression profiles within a panel of biomarkers, wherein each expression profile in the panel is associated with a subtype of breast cancer;
• diagnosing the subject with the triple negative breast cancer (TNBC) subtype of breast cancer when the differential expression in the isolated EVs positively correlates with a first expression profile of the panel of biomarkers, the first expression profile comprising overexpression of phosphorylated bruton tyrosine kinase (BTK) and equivalent expression of acetylated myosin heavy chain 9 (MYH9), both as compared to a control;
• or
• diagnosing the subject with the luminal A/B breast cancer (LAB) subtype of breast cancer when the differential expression in the isolated EVs positively correlates with a second expression profile of the panel of biomarkers, the second expression profile of the panel of biomarkers comprising overexpression of BTK and underexpression of MYH9, both as compared to a control;
• and
• administering, to the subject, a therapeutically effective dose of:
• an endocrine therapy comprising an aromatase inhibitor or an antiestrogen, when the subject is diagnosed with the LAB subtype of breast cancer;
• one or more of neoadjuvant chemotherapy, PARP inhibitors, and immunotherapy, when the subject is diagnosed with the TNBC subtype of breast cancer;
• or trastuzumab, when the differential expression correlates to a third expression profile associated with a third subtype of breast cancer comprising the HER2 subtype of breast cancer.